WIRELESS POWER TRANSFER
|PEWL1||A Fast Method for Generating Time-Varying Magnetic Field Patterns of Mid-Range Wireless Power Transfer Systems||Visualizing the magnetic flux paths for wireless power transfer systems enables researchers and engineers to understand the operations and design the geometrical dimensions of the practical systems. However, time-domain transient simulations of 3-D electromagnetic fields of complex wireless power transfer systems
with multiple coil-resonators are extremely time-consuming. This
paper describes a fast hybrid approach that combines the time domain
coupled circuit modeling and the magneto static analysis to form a fast time-domain analytical tool for studying complex wireless power transfer systems. The proposed methodology has been successfully applied to several wireless domino-resonator systems.
For the first time, the time-varying magnetic flux variations of wireless power domino-resonator systems can be visualized in computer simulations.
|PEWL2||Analysis and Tracking of Optimal Load in Wireless Power Transfer Systems||All the wireless power transfer (WPT) systems share a similar configuration including a power source, a coupling system, a rectifying circuit, a power regulating, and charging management
Circuit and a load. For such a system, both a circuit- and system-level analyses are important to derive requirements for high overall system efficiency. Besides, unavoidable uncertainties in a real WPT system require a feedback mechanism to improve the robustness of the performance. Based on the above basic considerations, this paper first provides a detailed analysis on the efficiency of a WPT system at both circuit and system levels. Under a specific mutual inductance between the emitting and receiving coils, an optimal load resistance is shown to exist for a maximum overall system efficiency. Then, a perturbation-and-observation based tracking system is developed through additional hardware
such as a cascaded boost-buck dc–dc converter, an efficiency sensing
System and a controller. Finally, a 13.56-MHz WPT system is demonstrated experimentally to validate the efficiency analysis and the tracking of the optimal load resistances. At a power level
of 40 W, the overall efficiency from the power source to the final load is maintained about 70% under various load resistances and relative positions of coils.
|PEWL3||A Methodology for Making a Three-Coil Wireless Power Transfer System More Energy Efficient Than a Two-Coil Counterpart for Extended Transfer Distance||A new methodology for ensuring that a three-coil wireless power transfer system is more energy efficient than a two coil counterpart is presented in this paper. The theoretical proof and the conditions for meeting the objective are derived and practically verified in a practical prototype. The key features of the magnetic design are to: 1) shift the current stress from the primary driving circuit to the relay resonator; and 2) generate a large relay current for maximizing magnetic coupling with the receiver coil for efficient power transfer. Consequently, the current rating and
cost of the driving circuit can be reduced and the overall quality factor and system energy efficiency are improved. This approach utilizes the combined advantages of the maximum efficiency principle and the use of relay resonator to overcome the energy efficiency
Problem for applications with extended energy transfer distances.